Glossary of Terms
Group of silicate minerals in the tectosilicates subclass composed only of silica (silicon dioxide - SiO2 ). The minerals in this group are all the varieties of Quartz, Chalcedony, Opal, Tridymite, and Cristobalite (as well as a few rarer forms of silicon dioxide). Although Opal contains water in addition to silica, it is nevertheless in the silica group.
The Silica Group is also known as the Quartz Group.